Periodic respiratory movements are necessary for ventilation in mammals. Many laboratories in the United States, Canada and Europe are devoting intense efforts to determine the central neural mechanisms underlying the production of periodic respiratory movements. The Symposium on CENTRAL NEURAL MECHANISMS PRODUCING PERIODIC RESPIRATORY MOVEMENTS has three aims: 1) to bring together researchers with diverse approaches to the study of different aspects of central neural production of respiratory movements in mammals. 2) To define and focus on the important questions that need to be answered in order to understand both normal and pathological states of respiratory movement production. This is a very timely issue. 3) to present and critically discuss research results, particularly in reference to the issues difined in 2). In order to focus this meeting, we will concentrate on those issues related to the determination of the biophysical properties of and the interactions between neurons underlying production of periodic respiratory movements.